IS-IS Support for MTR

The IS-IS Support for MTR feature provides Intermediate System-to-Intermediate System (IS-IS) support for multiple logical topologies over a single physical network. This module describes how to configure IS-IS for Multitopology Routing (MTR) for both unicast and multicast topologies.

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Prerequisites for IS-IS Support for MTR

Be familiar with the concepts in the “Routing Protocol Support for MTR” section.

Configure and activate a global topology configuration.

You must configure a multicast topology before activating the Intermediate System-to-Intermediate System (IS-IS) protocol in the multicast topology. For details, see the “MTR support for Multicast” feature module.

Activate a Multitopology Routing (MTR) topology on an IS-IS device.

Configure the MTR topology to globally configure all interfaces by using the
all-interfaces address family topology configuration command, or configure the IS-IS topology in interface configuration mode to configure only IS-IS interfaces. The order in which you perform the two tasks does not matter.

Restrictions for IS-IS Support for MTR

Only the IPv4 address family (multicast and unicast) and IPv6 address family unicast are supported. For information about configuring Multitopology IS-IS for IPv6, see the
IS-IS Configuration Guide.

Information About IS-IS Support for MTR

Routing Protocol Support for MTR

You must enable IP routing on the device for Multitopology Routing (MTR) to operate. MTR supports static and dynamic routing in Cisco software. You can enable dynamic routing per topology to support interdomain and intradomain routing. Route calculation and forwarding are independent for each topology. MTR support is integrated into Cisco software for the following protocols:

Border Gateway Protocol (BGP)

Enhanced Interior Gateway Routing Protocol (EIGRP)

Integrated Intermediate System-to-Intermediate System (IS-IS)

Open Shortest Path First (OSPF)

You apply the per-topology configuration in router address family configuration mode of the global routing process (router configuration mode). The address family and subaddress family are specified when the device enters address family configuration mode. You specify the topology name and topology ID by entering the
topology command in address family configuration mode.

You configure each topology with a unique topology ID under the routing protocol. The topology ID is used to identify and group Network Layer Reachability Information (NLRI) for each topology in updates for a given protocol. In OSPF, EIGRP, and IS-IS, you enter the topology ID during the first configuration of the
topology command for a class-specific topology. In BGP, you configure the topology ID by entering the
bgp tid command under the topology configuration.

You can configure class-specific topologies with different metrics than the base topology. Interface metrics configured on the base topology can be inherited by the class-specific topology. Inheritance occurs if no explicit inheritance metric is configured in the class-specific topology.

You configure BGP support only in router configuration mode. You configure Interior Gateway Protocol (IGP) support in router configuration mode and in interface configuration mode.

By default, interfaces are not included in nonbase topologies. For routing protocol support for EIGRP, IS-IS, and OSPF, you must explicitly configure a nonbase topology on an interface. You can override the default behavior by using the
all-interfaces command in address family topology configuration mode. The
all-interfaces command causes the nonbase topology to be configured on all interfaces of the device that are part of the default address space or the virtual routing and forwarding (VRF) instance in which the topology is configured.

Interface Configuration Support for MTR

The configuration of a Multitopology Routing (MTR) topology in interface configuration mode allows you to enable or disable MTR on a per-interface basis. By default, a class-specific topology does not include any interfaces.

You can include or exclude individual interfaces by configuring the
topology interface configuration command. You specify the address family and the topology (base or class-specific) when entering this command. The subaddress family can be specified. If no subaddress family is specified, the unicast subaddress family is used by default.

You can include globally all interfaces on a device in a topology by entering the
all-interfaces command in routing topology configuration mode. Per-interface topology configuration applied with the
topology command overrides global interface configuration.

The interface configuration support for MTR has these characteristics:

Per-interface routing configuration: Interior Gateway Protocol (IGP) routing and metric configurations can be applied in interface topology configuration mode. Per-interface metrics and routing behaviors can be configured for each IGP.

Open Shortest Path First (OSPF) interface topology configuration: Interface mode OSPF configurations for a class-specific topology are applied in interface topology configuration mode. In this mode, you can configure an interface cost or disable OSPF routing without removing the interface from the global topology configuration.

Intermediate System-to-Intermediate System (IS-IS) interface topology configuration: Interface mode IS-IS configurations for a class-specific topology are applied in interface topology configuration mode. In this mode, you can configure an interface cost or disable IS-IS routing without removing the interface from the global topology configuration.

(Optional) Displays IP traffic statistics for all interfaces or statistics related to the specified interface.

If you specify an interface type and number, information for that specific interface is displayed. If you specify no optional arguments, information for all the interfaces is displayed.

If the
topologyname keyword and argument are used, statistics are limited to the IP traffic for that specific topology.

The
base keyword displays the IPv4 unicast base topology.

Step 3

show ip traffic [topology {name |
all |
base}]

Example:

Device# show ip traffic topology VOICE

(Optional) Displays global IP traffic statistics (an aggregation of all the topologies when MTR is enabled) or statistics related to a particular topology.

The
base keyword is reserved for the IPv4 unicast base topology.

Step 4

clear ip interfacetype number [topology {name |
all |
base}] [stats]

Example:

Device# clear ip interface FastEthernet 1/10 topology all

(Optional) Resets interface-level IP traffic statistics.

If the
topology keyword and a related keyword are not used, only the interface-level aggregate statistics are reset.

If all topologies need to be reset, use the
all keyword as the topology name.

Step 5

clear ip traffic [topology {name |
all |
base}]

Example:

Device# clear ip traffic topology all

(Optional) Resets IP traffic statistics.

If no topology name is specified, global statistics are cleared.

Configuration Examples for IS-IS Support for MTR

Example: Activating an MTR Topology by Using IS-IS

The following example shows how to configure both the Multitopology Routing (MTR) topologies DATA and VIDEO and Intermediate System-to-Intermediate System (IS-IS) support for MTR. The DATA and VIDEO topologies are enabled on three IS-IS neighbors in a network.

“MTR Support for Multicast” feature module in the
Multitopology Routing Configuration Guide

Configure Multitopology IS-IS for IPv6

IP Routing: IS-IS Configuration Guide

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Feature Information for IS-IS Support for MTR

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

Table 1 Feature Information for IS-IS Support for MTR

Feature Name

Releases

Feature Information

IS-IS Support for MTR

12.2(33)SRB

Cisco IOS XE Release 2.5

This feature provides Intermediate System-to-Intermediate System (IS-IS) support for multiple logical topologies over a single physical network.

In Cisco IOS XE Release 2.5, support was added for the Cisco ASR
1000 Series Routers.

The following commands were introduced or modified:
address-family ipv4,
isis topology disable,
show isis neighbors,
topology.